The present invention relates generally to welding processes, and more particularly to weld joints and welding processes for welding finer metal particle control screens to compatible metallic structures for control screen assemblies adapted to mount on a perforated pipe used in a well.
It is well known to provide a particle control screen assembly for a perforated pipe used in a well, the assembly typically including at least one outer cylindrical perforated plate and at least one inner fine mesh control screen contained therein. For example, exemplary arrangements of particle control screen assemblies assembly for a perforated pipe used in a well are disclosed in U.S. Pat. Nos. 5,782,299, 5,899,271, and 5,937,944, all to Simone et al., and commonly owned by the present assignee of the instant patent application. Other arrangements of particle screen assemblies for a perforated pipe used in a well are disclosed in U.S. Pat. No. 5,411,084 to Padden, U.S. Pat. No. 5,232,048 to Whitebay, U.S. Pat. No. 4,064,938 to Fast. All six of these patents listed in the two preceding sentences are hereby incorporated by reference for the purpose of illustrating possible uses of the present invention as will later be more greatly appreciated.
In this art, it is desirable to minimize leakage of sand or other particulate into the perforated pipe for obvious reasons. As will be appreciated by those skilled in the art when viewing the present invention, the prior art attempts are deficient in minimizing leakage of sand or other particulate into the perforated pipe.
It is an objective of the present invention to further minimize leakage of sand and other particulate past particle control screen assemblies for a perforated pipe used in a well.
It has been discovered that the welding processes used in providing high strength permanent joints in particulate screen assemblies for a perforated pipe used in a well can tend to burn the thin wire material in the mesh screens due to the intense heat necessary for welding adjacent metal structures. This can occasionally result in the formation of gaps larger than the pore sizes in the screen and therefore the increased possibility of leakage of larger particles. The problem is particularly acute at weld locations between the particulate screen medium and a solid metal support structure. The present invention provides a solution to the problem through the arrangement of a sealing strip preferably in the form of a metal strip to cover the pores in the screen proximate the metal structure to which it is welded. The sealing strip ensures that large particles can not pass at locations near the weld regardless of whether or not wires of the mesh screen have been burned too extensively creating the possibility of gaps larger than the pore size of the mesh screen.
In the preferred embodiment, the sealing strip is a separate thin sheet of metal that is compatible with the welding metal used in the weld joint, and is arranged along the edge of the mesh screen prior to welding, such that the metal strip becomes integral or unitary with the weld joint. Prior to welding, the sealing strip may be bent around the mesh screen if desired, or may lie flat along the top or bottom surface of the screen.
Other object and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.